1. Technical Field of the Invention
The invention is directed to a locking device for engagement between stackable shipping containers to lock the containers together, wherein the locking device is engaged in an upper and lower conventional ISO aperture of corner castings on the containers to arrest their relative movement.
2. Prior Art
Automatic container locks have been in use with stackable shipping containers for over 20 years. Both hook locks and twist-head locks that have been each separately welded down on a flatcar to engage a single container have been used during this period. Automatic locks have also been designed to work between vertically stacked containers. However, none of these provide a combined spring-biased twist-head and hook lock engaged between the stacked containers with a compression pad extending past the edges of the stacked containers to house means for operating the twist-head and an indicator to alert the operator whether the spring-biased hook is an open or closed position. Further, all prior art automatic locks designed to lock together stackable containers must be removed in the same position that they were engaged to the container corner castings. Accordingly, prior art locks must be removed from the top of the bottom container while positioned on the shipping carrier or from the bottom of the top container while on the ground.
The primary object of the locking device according to the invention is directed to increasing an operator""s flexibility for respectively engaging or removing a lock during the stacking or unstacking of containers on which the lock is used.
Accordingly, the locking device according to the invention permits an operator at a loading terminal to engage the lock to the bottom of the top container while the container is on the ground or to the top of the bottom container when on a carrier before the upper container is loaded. In addition, at a discharge terminal an operator can chose to remove the lock from the top container of a stack by releasing the twist-head from engagement with the top container, with the lock still engaged in the lower container when the top container is unloaded, or alternatively, the top container can be unloaded with the lock still engaged and thereafter removed.
When the lock has been left engaged in the lower container after unloading of the top container, the spring-biased lock can be removed from the lower container by manually lifting the lock up from the engaged corner casting the height of its lower shear block and turning it 90xc2x0 in the corner casting to align the horizontal length of the hook with the longitudinal direction of the ISO aperture. This permits the lock to be further lifted up and completely disengaged from the corner casting without the need to compress the spring biased hook.
This flexibility allows operators at a loading terminal to do all lock engagement and removal on the carrier (stacked operation) and operators at an unloading terminal to do lock disengagement on the ground (wheeled operation) or vice versa.
This operational flexibility is achieved regardless of the original position in which the lock was fitted to the container enabling the operator at an unloading terminal to decide how to remove the lock instead of being required to pursue conventional practice. The invention also gives the operator an indicator showing the open or closed position of the hook that is clearly visible from the ground and from the platform at the end of the carrier. This is possible due to the extended compression pad that covers the container corner castings out past the side of the container. This extended load pad makes it also possible to direct the load force from the top container straight down into the stacking posts of the bottom container, thereby reducing the bending forces occurring with existing locks that have a compression load pad limited to surrounding the aperture hole of the engaged corner casting.
The lock according to the invention also gives the operator an alternative disengagement method in case the automatic lock malfunctions and does not open when the container is lifted. By pulling the handle operating the twist-head from the ground on the side of the carrier, the twist-head is turned to open, thus allowing the container to be unloaded in spite the malfunctioning hook side of the lock.